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1. Field of the Invention
This invention relates generally to pet doors, and more particularly to provide draft protection and insulation for minimizing heat transfer through the pet door, provision of means for locking the pet door, and improved ease of installation.
2. Background of the Invention
Prior art pet doors provide means for unassisted entrance to and/or exit from an enclosed location (such as a house, apartment, kennel, or pen) by a domesticated animal. Inventors have created several types of pet doors but none provide significant resistance to heat transfer, and most do not provide efficient weatherproofing. Use of these existing types of pet doors in non-temperate climates (either cold or hot climates) results in drafts and high amounts of heating or cooling energy loss. Additionally, security of the home can be compromised by installation of some of the existing pet doors, because the larger doors could be used by unauthorized humans to access the interior of the dwelling. Some prior art includes disclosures to provide locking mechanisms, but these are either inadequately strong to prevent a determined human from entering, or are needlessly complex and therefore expensive to produce. Finally, some existing pet doors and prior patent art doors are difficult to install by the homeowner, since they require cutting of an appropriate hole and usually drilling of several holes through the door or wall, through which difficult blind insertion of fasteners must be accomplished.
U.S. Pat. No. 2,758,646 to Johnson (1956) discloses a basic type of pet door comprised of two flexible flaps mounted on their upper edges to a frame. One flap is larger and has a hole covered by the other flap, so the animal can push open both flaps going one way, but steps through the hole and pushes open only the smaller flap going through in the other direction. One embodiment shows an arrangement of two double flaps to improve the draft and weather resistance of the design. This design is inefficient at providing an insulated barrier for heat transfer, since at best it would provide an air space subject to convection air currents and attendant heat transfer. In practice, the flexible materials utilized in current commercial designs of this type tend to warp in hot conditions and become too stiff to properly close in cold conditions, leading to air flow, ice formation, and high heating or cooling losses through the door. An improvement to this door, U.S. Pat. No. 3,690,299 to Johnson (1972), did not address either of these problems. This patent also discloses a solid thin panel that may be inserted to prevent entry by the animal, but this is not sufficient for preventing entry by humans.
U.S. Pat. No. 2,839,791 to Lee (1958) shows a spring mounted single door that can be pushed open in either direction. This design will tend to stay ajar rather than completely close after the animal pushes through, allowing air flow through the door. This design is also not amenable to a significant amount of insulation.
U.S. Pat. No. 3,138,829 to Grose (1964) discloses a two way rigid dog door that hinges on a vertical side. The spring-loaded hinges tend to return the doors to the closed position, but the door provides no significant insulation. A further problem with the horizontally hinged door arises when an animal goes only partway through the door, then changes its mind and tries to back up. When this happens, the door will tend to close on and trap the animal, causing it distress and possibly injury.
U.S. Pat. No. 3,978,616 to Pennock (1976) shows a rigid two-way door hinged on the upper edge, with spring-loaded cams operating on the upper door surface for holding the door in a vertical, closed position. This design does not address the need for weatherproofing the edges or insulation of the door itself.
U.S. Pat. No. 4,134,232 to Dodge et al. (1979) discloses another horizontally hinged door, with tension springs providing the force to keep the door closed. This spring-closure design would have a greater tendency to close on animals if they attempt to back up rather than go all the way through, causing the problems discussed above. The door also is not designed to provide any significant amount of insulation to prevent heat transfer.
U.S. Pat. No. 4,480,407 to Needham et al. (1984) discloses a method for magnetically closing flexible or rigid flap type doors. While this can provide an improvement in terms of weather tightness of the doors, it does not address the low insulating problems, and also adds expense to production of a door, since the design requires mating magnetic members. Also, the deformation of flexible doors in extreme heat or cold can overcome the ability of magnets to seal the gap.
U.S. Pat. No. 4,776,133 to Green (1988) discloses a locking mechanism to prevent door opening in one or both directions, but the mechanism is not strong enough to prevent forced entry by a determined human being.
U.S. Pat. No. 4,833,828 to Gingrande (1989) discloses a spring-return pet door design that is hinged horizontally in the middle of the door. While this possibly addresses some of the weather proofing and draft prevention issues, the mechanism requires the animal to enter and exit on opposite sides of the hinge, which would increase the difficulty of training the animal to use the door. More importantly, the required surface area of the invention is twice that for a double-acting single door, which increases the area of heat transfer. This design makes no claims of insulation possibilities. U.S. Pat. No. 5,581,940 to Peterson (1996) poses similar problems.
U.S. Pat. No. 4,840,217 to Evans (1989) discloses a design that is comprised of two separate doors, each of which opens only in one direction. This requires training an animal to pry open one door and push through the other. This training would be beyond most pet owner""s capabilities, not to mention most pet""s abilities.
U.S. Pat. No. 5,735,079 to Davlantes (1998) and U.S. Pat. No. 5,946,856 to Davlantes (1999) describe embodiments of the sliding panel type security door that is held along its edges by channels. This arrangement is not strong enough to prevent forced entry by a human being.
The prior art does not provide a pet door design that includes significant insulating characteristics, weather tightness, positive door closure, means of securely locking the door, and ease of use by the animal, and ease of installation for the owner in one configuration.
Accordingly, several objects and advantages of the present patent application are:
to provide a bi-directional door that is easily operated by a domestic animal to exit or enter an enclosed space;
to provide a door designed to tightly and positively close when not in use to prevent air flow and drafts, to be resistant to opening by wind, and to be weatherproof to rain, sleet, or snow;
to provide a door that incorporates significant thickness of insulating material so the door is an effective impediment to heat transfer without increasing the difficulty of operation by the animal;
to provide a simple but robust means of locking the pet door to prevent unauthorized entry by humans or other animals;
to provide a design which makes installation of a pet door easier for the installer;
to provide a door design that is adjustable for installation in a variety of exterior doors or thicker wall sections without modification; and
to provide a design that can be manufactured for relatively low cost.
Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description.
In accordance with the present invention a pet door is comprised of an interior and exterior frame suitable for mounting in a hole cut in an exterior door or wall; a spacer providing an extended tunnel for thicker wall sections; an insulating core for the interior frame; an interior door that opens in only one direction; an insulated outer door that opens in both directions but closes against the inner door; and a locking bar mechanism that secures both doors in the closed position. Both the inner and outer doors are shut at opposing non-vertical angles, which allows the weight of each door to provide a constant closing torque operating to maintain closure until counteracted by force provided by the entering or exiting domestic animal.